The objectives of this research program are to continue our studies into the understanding of the mechanisms of action of Escherichia coli heat-labile enterotoxins on adrenal tumor cells in tissue culture and of their role in diarrheal disease of man. The goals will be accomplished by immunochemical and physicochemical characterization of a purified E. coli enterotoxin, and delineation of the toxin's molecular interactions with adrenal tissue-cultured cells at the cellular and membrane levels. The important antigenic, binding, and toxic moieties of the toxin will be identified, as will be the membrane receptor components. Eventually, such determinants may prove useful in preventing or modifying the toxin's effects in in vivo models. Seroepidemiologic investigations will be continued, with a special emphasis on delineating the optimal conditions for the processing and storage of fecal specimens containing enterotoxigenic E. coli.